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Related Concept Videos

Phosphoinositides and PIPs01:42

Phosphoinositides and PIPs

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Phosphoinositides are a group of phospholipids containing a glycerol backbone with two fatty acid chains and a phosphate attached to a myoinositol sugar ring. The inositol head group extends into the cytoplasm, where it is modified by adding phosphate groups to form phosphatidylinositol phosphates or PIPs.
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IP3/DAG Signaling Pathway01:11

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Membrane lipids such as phosphatidylinositol (PI) are precursors for several membrane-bound and soluble second messengers. Specific kinases phosphorylate PI and produce phosphorylated inositol phospholipids. One such inositol phospholipids are the  phosphatidylinositol-4,5 bisphosphate [PI(4,5)P2], present in the inner half of the lipid bilayer. Upon ligand binding, GPCR stimulates Gq proteins to turn on phospholipase Cꞵ. Activated phospholipase Cꞵ cleaves PI(4,5)P2 and...
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Amplifying Signals via Enzymatic Cascade01:22

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When a ligand binds to a cell-surface receptor, the receptor's intracellular domain changes shape, which may either activate its enzyme function or allow its binding to other molecules. The initial signal is amplified by most signal transduction pathways. This means that a single ligand molecule can activate multiple molecules of a downstream target. Proteins that relay a signal are most commonly phosphorylated at one or more sites, activating or inactivating the protein. Kinases catalyze...
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The JAK-STAT Signaling Pathway01:20

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Several cytokine receptors have tightly bound Janus kinase or JAK proteins attached at their cytosolic tail. Small signaling molecules such as cytokines, growth hormones, or prolactins bind to the cytokine receptors and initiate their dimerization. The dimerization brings the cytosolic JAKs together that trans-phosphorylate and activates each other. The activated JAKs now phosphorylate cytosolic tails of the cytokine receptors, which serve as binding sites for adaptor proteins such as  SH2...
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The mammalian target of rapamycin  (mTOR) is a serine/threonine kinase that regulates growth, proliferation, and cell survival in response to hormones, growth factors, or nutrient availability. This kinase exists in two structurally and functionally distinct forms: mTOR complex 1  (mTORC1) and mTOR complex 2  (mTORC2). The first form (mTORC1) is composed of a rapamycin-sensitive Raptor and proline-rich Akt substrate, PRAS40. In contrast,  mTORC2 consists of a...
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Amplifying Signals via Second Messengers01:15

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Many receptor binding ligands are hydrophilic; they do not cross the cell membrane but bind to cell-surface receptors. Thus, their message must be relayed by second messengers present in the cell cytoplasm. There are several second messenger pathways, each with its own way of relaying information. For example, the G protein-coupled receptors can activate both phosphoinositol and cyclic AMP (cAMP) second messenger pathways. The phosphoinositol pathway is active when the receptor induces...
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Related Experiment Video

Updated: Apr 21, 2026

Identification of Inositol Phosphate or Phosphoinositide Interacting Proteins by Affinity Chromatography Coupled to Western Blot or Mass Spectrometry
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Localized phosphoinositide metabolism regulates STIM1/ORAI1 fast inactivation.

Ning Dai1, Shawn M Lamothe2, Jody Groenendyk1

  • 1Department of Biochemistry, University of Alberta, Edmonton, AB T6G 2H7, Canada.

Iscience
|April 20, 2026
PubMed
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Myotubularin-related protein 7 (MTMR7) regulates calcium influx by interacting with STIM1 and altering plasma membrane lipids. This interaction fine-tunes ORAI1 channel inactivation, impacting cellular calcium homeostasis.

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Radiolabeling and Quantification of Cellular Levels of Phosphoinositides by High Performance Liquid Chromatography-coupled Flow Scintillation
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Identification of Inositol Phosphate or Phosphoinositide Interacting Proteins by Affinity Chromatography Coupled to Western Blot or Mass Spectrometry
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Fluorescence-Based Measurements of Phosphatidylserine/Phosphatidylinositol 4-Phosphate Exchange Between Membranes
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Radiolabeling and Quantification of Cellular Levels of Phosphoinositides by High Performance Liquid Chromatography-coupled Flow Scintillation
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Area of Science:

  • Cellular Biology
  • Molecular Biology
  • Physiology

Background:

  • Store-operated Ca2+ entry (SOCE) is crucial for cellular calcium (Ca2+) homeostasis.
  • SOCE is initiated by endoplasmic reticulum (ER) Ca2+ depletion, activating stromal interaction molecule 1 (STIM1) and ORAI1 channels.

Purpose of the Study:

  • To investigate the role of myotubularin-related protein 7 (MTMR7) in regulating ORAI1 inactivation during SOCE.
  • To elucidate the mechanism by which MTMR7 influences ORAI1 activity and Ca2+ influx.

Main Methods:

  • Co-immunoprecipitation to assess STIM1-MTMR7 complex formation.
  • Measurement of Ca2+ influx using fluorescent Ca2+ indicators.
  • Biochemical assays to determine phosphoinositide levels (PI(3,5)P2 and PI(4,5)P2).

Main Results:

  • STIM1 forms a complex with MTMR7, which is localized to ER-plasma membrane contact sites.
  • MTMR7 modulates plasma membrane phosphoinositide levels, promoting ORAI1 inactivation and reducing SOCE.
  • Loss of MTMR7 catalytic activity or disruption of STIM1-MTMR7 interaction impairs ORAI1 inactivation and enhances SOCE.

Conclusions:

  • The MTMR7/STIM1 complex acts as a novel regulator of ORAI1 inactivation.
  • Phosphoinositide signaling at ER-plasma membrane contact sites fine-tunes SOCE.
  • This study reveals a new mechanism controlling cellular Ca2+ entry and homeostasis.